Embodiments of the invention relate generally to devices for switching current, and more particularly to microelectromechanical switch structures.
A circuit breaker is an electrical device designed to protect electrical equipment from damage caused by faults in the circuit. Traditionally, many conventional circuit breakers include bulky (macro-)electromechanical switches. Unfortunately, these conventional circuit breakers are large in size may necessitate use of a large force to activate the switching mechanism. Additionally, the switches of these circuit breakers generally operate at relatively slow speeds. Furthermore, these circuit breakers can be complex to build and thus expensive to fabricate. In addition, when contacts of the switching mechanism in conventional circuit breakers are physically separated, an arc can sometimes form therebetween, which arc allows current to continue to flow through the switch until the current in the circuit ceases. Moreover, energy associated with the arc may seriously damage the contacts and/or present a burn hazard to personnel.
As an alternative to slow electromechanical switches, relatively fast solid-state switches have been employed in high speed switching applications. These solid-state switches switch between a conducting state and a non-conducting state through controlled application of a voltage or bias. However, since solid-state switches do not create a physical gap between contacts when they are switched into a non-conducting state, they experience leakage current when nominally non-conducting. Furthermore, solid-state switches operating in a conducting state experience a voltage drop due to internal resistances. Both the voltage drop and leakage current contribute to power dissipation and the generation of excess heat under normal operating circumstances, which may be detrimental to switch performance and life. Moreover, due at least in part to the inherent leakage current associated with solid-state switches, their use in circuit breaker applications is not possible.
Micro-electromechanical system (MEMS) based switching devices may provide a useful alternative to the macro-electromechanical switches and solid-state switches described above for certain current switching applications. MEMS-based switches tend to have a low resistance when set to conduct current, and low (or no) leakage when set to interrupt the flow of current therethrough. Further, MEMS-based switches are expected to exhibit faster response times than macro-electromechanical switches.